The Structure of the Earth (Junior Cert Geography): Revision Notes

The Structure of the Earth

Structure of the Earth

The Earth is made up of three main layers: the crust, the mantle, and the core. Each layer is different in thickness, material, and temperature.

• Crust: The outermost layer of the Earth.
  • Made of solid rock.
  • It is about 5–10 km thick under the oceans and around 30–60 km thick under the continents.
  • The crust is where we live, and it includes the land, oceans, and mountains.

• Mantle: The layer just beneath the crust.

  • Made of very hot rock. Some parts are semi-molten and contain magma.
  • Temperatures can reach up to 4,000°C.
  • Slow movements in the mantle cause tectonic plates to move, which can lead to earthquakes and volcanoes.

• Core: The innermost part of the Earth.

  • Divided into two parts: the outer core and the inner core.
  • Outer core: made of molten (liquid) metals, mainly iron and nickel.
  • Inner core: solid, because the pressure at the centre of the Earth is so strong it forces the metals to stay solid even though the temperature is over 5,000°C.